Fused salt electrolysis cell



J. V. CARLISLE FUSED SALT ELECTROLYSIS CELL Aug. 11, 1953 4 Sheets-Sheet1 Filed July 15, 1950 INVENTOR.

JAMES V. CARLISLE BYWW 1953 J. v. CARLISLE 2,643,631

F USED SALT ELECTROLYSIS CELL Filed July 13, 1950 tqSIlGGbS-SIXGGT. 2

FIG. 3

INVENTOR.

JAMES V. CARLISLE Aug. 11; 1953 J. v. CARLISLE v F USED SALTELECTROLYSIS CELL 4 Sheets-Sheet 5 Filed July 15, 1950 FIG. 5

FIG. 4

FIG. 8

FIG. 6

INVENTOR JAMES v. CARLISLE BY 2 2 Q P 4 Sheets-Sheet 4 J. V. CARLISLEFUSED SALT ELECTROLYSIS CELL FIG 9 Aug. 11, 1953 Filed July 15, 1950INVENTOR.

JAMES v CARLISLE BYMW FIG.

FIG. IO

f atented Aug. 11, 1 953 FUSE-D SALTIELECTROLYSIS CELL James V.Carlisle, Baton Rouge, La., assignor to Ethyl Corporation, New York,

ration of Delaware N. Y., a =corpo- Application July 13,1950, Serial No.173, 71

This invention relates to an electrolysis cell for the production ofchlorine andsodium b'y the electrolysis of sodium chloride in a moltencondition. More particularly, the invention relates to an improved anodeassembly and cell bottom for cells of the Downs type.

The Downs type electrolysis cell (U. S. Patent 1,501,756) ischaracterized by a centrally positioned vertical graphite anode and asurrounding steel cathode of cylindrical shape. These electrodes definea narrow annular space within which the electrolysis occurs. Acylindrical diaphragm of wire screen is positioned within this space,concentric with the anode and cathode, for the purpose of preventingrecombination of the sodium and chlorine molecules after their releaseat the cathode and anode, respectively.

As both the chlorine and sodium produced by electrolysis rise in theelectrolyte, it is necessary to have a fairly complicated cover withmeans for separate collection of these products. Hence, the centrallypositioned graphite anodes are normally connected to a source ofelectrical energy through the bottom of the cell. In the past, it hasbeen the practice to build the cells with the anode actually projectingbelow the cell bottom. The bottom of the cell has previously beenconstructed by forming a bottom wall of refractory cement from the anodeto the wall of the cell. lhe cement layer rested on a base platecontaining a hole through which the anode projected.

While in general operable and satisfactory, the former cells,constructed as above described, are deficient in several respects. Theanodes were fastened to a casting which in turn was bolted to a copperbus-bar. The bolting of the anode to a steel connector subjected thegraphite to severe stresses. These joint conditions cause such severestresses on the anode graphite that at times fractures occur,necessitating expensive replacement and rebuilding of the cell. Not onlyare the anodes subjected to severe mechanical stress, but the cells areprone to develop leaks at the joint between the cell bottom and theanode.

An object of the present invention is to provide a cell with an improvedanode assembly. Another object is to provide a cell with improved andmore lasting electrical connections to the anode. A further object is toprovide an anode assembly which makes possible precise registration andvertical alignment of the anodes inassembly, while minimizing the amountof machining heretofore required. One more object is to Claims. (Cl.204-243) make possible the use of round graphite electrode stock,thereby'achieving'large economies in the initial cost of materials ofconstruction for the cell.

The invention, broadly speaking is a cell bottom and anode assemblycomprising a liquid tight metal base pan and .one or more verticalanodes resting thereon, male and female means on the anode base and thebase pan registering the anode in a horizontal plane and additionalclamping means, attached to the" base pan, retaining the anode invertical alignment. The base pan-is adapted to" carry the cell currentwhich is transmitted to the anode through a body of low melting metalsurrounding at least 'in part the portion ofthe anode within thevertical confines of the bjase pan. An impermeable membrane of refactorymaterialseals the metal parts of the assembly from contact with thefused electrolyte of the cell. In preferred forms of the invention, ametal plate rests on the base pan beneath the refractory membrane, andsnugly surrounds the anode, except at points where the clamping meansare provided. .Such plates insure that a small expansion space can bemaintained above the low melting metal surrounding the anode base. 1

Numerous embodiments are possible as will appear hereafter. In thepreferred embodiments, the means for providing horizontal registrationis permissive of a limited movement of an anode in vertical planes aboutsaid registration point.

The invention will be more easily understood from the detaileddescription given hereafter and the accompanying drawings. Referring tothe drawings: 1

Fig. 1 is a sectional elevation view of a Downs type cell incorporatingan embodiment of the invention. Figure 2 is a cross sectional plan viewof the bottomof the cell of Fig. 1. A cut away portion shows theconstruction details of the anode retaining means, below the finalsealing membrane of refractory cement'which comprises the bottom' of thecell interior and retains the fused electrolyte bath. Figs. 3, 5, 6 and'l 'are elevation drawings showing details of additional embodiments,particularly ofthe anode at thezone of contact with the retaining meansproviding vertical alignment.

Figs. 4 and 8 show plan views of anode and retaining means of Figs 3 and5 respectively, and illustrate the manner in which the anoderetainingdevice can'be varied.

' Figs. 9 and 11 are elevation views showing different methods by whichthe anodes are properly registered in a horizontal plane but limitedradial adjustment is still permitted.

Fig. 10 is a plan view showing the disposition of the supporting andregistering elements of Fig. 9.

Referring to Figs. 1 and 2, an anode l and a concentric cathode 2 arecentrally mounted within the cell interior which is bounded by side wall3 and a refractory bottom I3. The base pan 4 contains a central recessor socket for receiving the anode shank H, an extended lip or rim 5which provides the foundation for side wall 3, and a connector block 54protruding at the bottom. The recess in the pan for anode shank II hasan inverted cone bottom, thereby automatically registering in horizontalplan the anode l by means of the spherically cut bearing surface 25.Segmental clamps 6, I, 8 and 9 are fastened b bolts It] to pan 4.

The anode shank H is surrounded by lead metal IE, or other relativelylow melting metal, which preferably does not fill the complete depth ofthe annular space between the anode shank I l and the base pan 6. Asmall expansion space 23 is left when the lead metal I2 is poured. Athin metal plate 24 laid on the top surface of the pan surrounds theanode and fits fairly snugly, except at points at which it is recessedor notched to provide space for the anode clamps 6, l, 3, 9. A layer ofmolded refractory covers plate 24 and clamps 6, l, 8 and 9.

In assembly, a small amount of molten metal is introduced into pan 4 andthe anode is lowered into place. The anode is easily registered orcentered with the anode pan by means of the centering action of thespherical surface of the anode and the inverted conical bottom of thepan 5. The anode is then adjusted if necessary by limited movement in avertical plane about the bearing end on the pan, to provide precisevertical alignment with respect to the plane of the top of the pan. Themetal plate 24 and several clamps are put in place, the clamps beingsecurely fastened down with the attaching bolts. At least one clamp isleft unattached to permit molten lead or other low melting metal to bepoured in the annular space between the anode shank H and the pan 4. Asheretofore described, the quantity of molten metal is insufiicient tocompletely fill the annular space, a small space being normally left asan expansion zone.

The final clamp is then secured in place and the molten metal allowed tosolidify and cool. After solidification of the metal, the cell wall isbuilt and then a layer of refractory cement is poured in the cell andallowed to set, forming a sealing and protective layer 13 between allthe metal parts in the anode assembly and the fused electrolytecontained in the operating cell.

Electrical power is supplied to the cell through copper bus bars 22which are bolted to the connector block I4, the latter forming anintegrally cast part of the pan. The cell is supported by structuralsteel members I5 which support, through insulator blocks It the pan andthe rest of the cell structure. The cell wall 3 is surrounded andstrengthened by a steel shell i8, which, however, does not makeelectrical contact with the base pan rim 5. A retaining ring 25 weldedto the rim 5 is beneficial in strenghening and aligning the lowerportion of the cell wall 3. The cathode 2 is inserted in place as thecell wall 3 is being constructed, and is separated by insulatingmaterial ll from electrical contact with the steel outer jacket l8.

The collector dome i9 and diaphragm 29 are inserted into the cellstructure as a unit, the diaphragm being carefully positioned so as tobe concentric with the anode l and the cathode 2.

It will be apparent from Fig. 1 that the precise vertical disposition ofanode I is of great importance in obtaining the desired uniformelectrolysis zone comprising the annular space between the anode andcathode. Precise location of anodes in a horizontal plane, and verticalalignment thereof, is especially important in cells using a plurality ofanodes. In such cells, the anodes must not only be accurately alignedwith respect to the cathodes, but also with respect to each other. Theanode assembly of the present invention is ideally suited for suchplural electrode cells.

Numerous variations in the anode assembly are possible within the scopeof the invention. All embodiments are characterized by coactingregistration means on the anode and base pan, respectively, and bysupplementary retaining means adjustabl attached to the base pan andsecuring the anode in assembly. In a preferred embodiment, as alreadydescribed with reference to Figs. 1 and 2, the registration means arepermissive of limited movement in a vertical plane during assembly.Various modifications of the anode assembly, particularly with respectto coaction with the vertical retaining means, are illustrated by Figs.3, 4, 5, 6, '7 and 8.

Referring to Figure 3, this embodiment shows an anode embodiment whichis the most economical design possible with respect to utilization ofgraphite or carbon for the anode. The anode is of uniform diameter inits entire length, with the exception of a shallow circumferentialrecess in the form of a skewed V 27. A split ring formed of two segments28 and 29 encircles the anode 3G and bears on the lower frusto-conicface of circumferential V 27. Fig. 4 gives a plan view of Fig. 3, andshows the disposition of bolts 3| adjustably attaching segments 28 and29 to the base 32. Segments 28 and 29 can be joined by bolts 33 throughupright lips 34 in adjacent relationship on segments 28 and 29. Theworking faces of the ring segments 28 and 29, in contact with the basecasting 32 are accurately machined for ease in adjustment of theassembly.

Additional anode designs are illustrated by Figs. 5, 6, and '7.Referring to Fig. 5, shank section 35 of the anode joins the upper orelectrolyzing section 38 by a curved shoulder 31. This design isparticularly suitable for anodes of relatively small diameter. The useof a curved shoulder minimizes the likelihood of stress concentration atsharp intersections, which would place an undue stress on the anodestock.

The anode illustrated by Fig. 6 represents the simplest type ofconstruction for the invention. A shank portion 38 joins theelectrolyzing section 40 by a shoulder 39 of frusto-conic section cut atabout 45 degrees to the axis of the anode. This design is easilymanufactured from graphitestock of the same diameter as the shank 38.

The anode represented by Fig. 7 is particularly advantageous forembodiments of the invention when the metal surrounding the anode issolid. In this anode, one or more circumferential grooves M are cut inthe shank portion 42. In assembly, as molten metal is poured around theanode and subsequently solidifies, the anode is more firmly anchored inproper alignment in the cell. Such grooves are also of particularbenefit g in securing strength and rigidity in the constructioncf acell.

Fig. 8 is a plan View of the simplest type of retaining means forsecuring and fastening the anodein vertical position. Thisretainingmeans comprises a one piece ring with a similar cross sectionto the two piece retaining collar illustrated by Figs. 3 and 4. Thisform of retaining means is especially suitable for anodes having anenlarged .shank, as illustrated by Figs. '6 and 7. The inner diameterof-such .a retaining device is preferably of greater diameter than theelectrolysis section of the anode A5.

The anodes for use in the invention can be varied widely with respectto'the meansifor engaging with the adjustable rings -or segments, asabove described. In additiomnumerous variations are possible withrespect to the bearing end .of the anode which cooperates with the-basepan to obtain positive and accurate registration in a horizontal plane.As already mentioned, the assembly utilizes male and female means on theanode bearing end and the base pan. The preferred registration meanswill permit limited movement of an anode in a vertical plane about thebearing point in assembly, although this feature is not absolutelyessential. It is necessary, however, for the anode base or bearing endto be accurately registered in the horizontal plane.

Examples of alternate means of providingregistration in a horizontalplane for the anode bearing end are given by Figures 9, 10 and 11.Figures Qand lilare, respectively-sectional elevation-and plan views-ofa registration means employing a centering pin integrally cast in thebase pan. Figure 11 illustrates registration means which also providessupport for the anode.

Referring to Figures 9 and 10, a pin is cast integrally with base 52 andcenters anode 53 by engaging with hole 5 3. The anode base face ismachined fiat and rests on the machined upper faces of ribs 55. Theribs55 provide an accurate seat for the anode and permit molten metal toflow around this surface in assembly. In this embodiment, verticalalignment is primarily achieved by the accurate machining of the anodebase and the supporting ribs 55.

Another suitable registration and support means is shown by Figure 11,which is a sectional elevation view of the joint of an anode and a basepan. Referring to the figure, a portion of the base pan 6-3 is shown,and the base or hearing end 61 of the anode. An approximately sphericalprotrusion 54 is machined on the base pan, and coincides with a conicalrecess in the end of the anode, registering thel anode in horizontalposition. A slot 62 facilitates passage of molten metal to all parts ofthe anode shank in assembly.

It will be apparent from the foregoing description that a large numberof combinations of specific means are possible for different embodimentsof the invention. Thus, any of the several anode bearing and designsheretofore shown may be combined with any of the means which retain theanode and also provide for radial adjustment during assembly. Differentcombinations will be preferred for different cell sizes or designs. Forexample, if the anode is a foot or more in diameter, the use ofsegmental clamps such as shown in Figure 2, are preferred for providingradial adjustment and vertical alignment. On anodes of the specieshaving a shank or bearing end of larger diameter than the electrolysis.end, :a zone apiece ..retai-ning means isssuitable.

The electricalefficiency "of the anode assembly, with respect tomaintaining :alow voltage drop, is assured by :the 'use .of a poured.metal joint. surrounding the .anode shank'zand. contacting the base;.pan. The :metal utilized :for'this purpose should, preferably, bea:relatively low melting 'material, of high -electrical conductivity. Agdesirable characteristic .is that *the .metal should .shrink .on ;the.anode shank in :solidificae tion, thereby grip-ping securely atheranodeand providinggood electrical contactat all points. Lead and :tin aresuitable elemental imetals. Various low .:melting alloys are also quite.satisfactory, especially those containing appreciable proportions oflead; for example solders and type'metals. 'The preferred-metaliiselemental leader-solder. If an alloy is -used,it1is preferred that itshould :not contain appreciable .amounts of metals vof high vaporpressure, :for example, mercury, sodium or bismuth should beavoided.

The operating conditions of: the cell,.the specificproportions vofthebase pan, and vtheimetal used'for .electrical contact between theanode and the base pan maybe such that the ;metal is either solid orfused. during: operation. .Either mode of operation is satisfactory.Ingeneral, however, it will be preferred to operate-with a molten metalsurrounding the anode and filling the base pan. Although theelectrical-conductivity of amolten metal is lessthan -fora solid metal,the actual voltage drop and consequent power loss in the metal isinsignificant-in comparison to the-losses-which normally occur at thejunction of two solids. Theoverallpower loss involved in passing currentthrough'the base pan and a molten metal "to'the carbon anode isthereforesubstantially less than occurs if the metal is .in the solid phase.

Havingfully described the invention and embodiments thereof, what Iclaim is:

1. In a fused salt electrolysis cellcharacterized by a bottom mountedanode, the improved bottom and anode assembly comprising a liquid-tightmetal base pan adapted to carry the cell current, avertical anode ofcircular cross-section having a relatively shortvertical-portion'thereof consisting of af-rusto-conicsection, alongitudinal section of said frusto-conic section forming an acute angleto the vertical, said frusto-conic section being adjacent the uppersurface of the base pan, a body of low melting metal, and a plurality ofarcuate clamps having internal bearing faces, the said faces beingportions of a frusto-conic section substantially corresponding to thefrustoconic section of the anode, the pan having a socket receiving thelower end of the anode, said socket being larger in lateral area thanthe anode, but having integral registration means at the lower partcontacting and centering the an-- ode end in a lateral plane, the bodyof low melting metal partially filling the space in the socket notoccupied by the anode, the clamps surmounting and attaching to the panand retaining the anode in vertical alignment.

2. In a fused salt electrolysis cell characterized by a bottom mountedanode, the improved bottom and anode assembly comprising a liquid-tightmetal base pan adapted to carry the cell current, a vertical anode ofcircular cross section and having a peripheral groove, at least thelower side of said groove being a, frusto-conic section, a longitudinalsection thereof forming an acute angle to the vertical, said groovebeing adjacent the upper surface of the base pan, a body of low meltingmetal, and a plurality of arcuate clamps having internal bearing faces,the said faces being portions of a frusto-conic section substantiallycorresponding to the frusto-conic section formed by the lower side ofthe anode groove, the pan having a socket receiving the lower end of theanode, said socket being larger in lateral area than the anode, buthaving integral registration means at the lower part contacting andcentering the anode end in a lateral plane, the body of low meltingmetal partially filling the space in the socket not occupied by theanode, the clamps surmounting and attaching to the pan and retaining theanode in vertical alignment.

3. In a fused salt electrolysis cell having a bottom mounted anode, theimproved bottom and anode assembly comprising a liquid-tight metal basepan adapted to carry the cell current, a vertical anode of circularcross section and having a peripheral groove, at least the lower side ofsaid groove being a frusto-conic section, a longitudinal section thereofforming an acute angle to the vertical, said groove being adjacent theupper surface of the base pan, a body of low melting metal, and aplurality of arcuate clamps having internal bearing faces, the saidfaces being portions of a frusto-coni-c section substantiallycorresponding to the frusto-conic section formed by the lower side ofthe anode groove, the total are lengths of the clamps approaching theperipheral length of the groove, the pan having a socket thereinreceiving the lower end of the anode, the socket being larger in lateralarea than the anode but having integral registration means at the lowerpart thereof contacting and centering the anode end in a lateral planebut not in themselves preventing limited movement of the anode in avertical plane about the anode bottom, the body of low melting metalpartially filling the space in the socket not occupied by the anode, theclamps surmounting and being attached to the pan and retaining the anodein vertical alignment.

4. In a fused salt electrolysis cell having a bottom mounted anode, theimproved bottom and anode assembly comprising a liquid-tight metal basepan adapted to carry the cell current, and having a socket receiving thelower end of the anode, a vertical anode mounted in the socket ofcircular cross section and having a peripheral groove, the lower side ofsaid groove being a frusto-conic section, a longitudinal section thereofforming an acute angle to the vertical, said groove being adjacent theupper surface of the base pan, the socket being larger in lateral areathan the anode, the socket and anode end having integral male and femaleregistration contacting means centering the anode end in the socket butnot in themselves restricting the anode from limited movement in avertical plane about the centered anode end, a body of low melting metalpartially filling the space in the socket not occupied by the anode, aplate upon the pan surface snugly surrounding the anode at the point ofprojection from the socket except for a plurality of notches, aplurality of arcuate clamps surmounting and adjustably attached to thebase pan and clamping the anode in vertical alignment, the clampscorresponding in number and being placed in the notches in said plate,the said arcuate clamps having internal bearing faces, the said facesbeing portions of a frustoconic section substantially corresponding tothe frusto-conic section formed by the lower side of the anode groove,the total are lengths of the clamps approaching the length of thegroove, and a sealing membrane of refractory impermeable to fused saltsealing the plate and clamps from contact with the fused saltelectrolyte.

5. The apparatus of claim 1 further defined in that the lower end of theanode is in the form of a hemisphere and the integral registration meansin the socket in the pan is an inverted conical depression.

JAMES V. CARLISLE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 510,276 Lyte Dec. 5, 1893 2,213,073 McNitt Aug. 27, 19402,370,087 Stuart Feb. 20, 1945 2,592,483 Smith et a1 Apr. 8, 1952FOREIGN PATENTS Number Country Date 146 Great Britain Apr. 31, 190640,354 Germany Aug. 15, 1886

1. IN A FUSED SALT ELECTROLYSIS CELL CHARACTERIZED BY A BOTTOM MOUNTEDANODE, THE IMPROVED BOTTOM AND ANODE ASSEMBLY COMPRISING A LIQUID-TIGHTMETAL BASE PAN ADAPTED TO CARRY THE CELL CURRENT, A VERTICAL ANODE OFCIRCULAR CROSS-SECTION HAVING A RELATIVELY SHORT VERTICAL PORTIONTHEREOF CONSISTING OF A FRUSTO-CONIC SECTION, A LONGITUDINAL SECTION OFSAID FRUSTO-CONIC SECTION FORMING AN ACUTE ANGLE TO THE VERTICAL, SAIDFRUSTO-CONIC SECTION BEING ADJACENT THE UPPER SURFACE OF THE BASE PAN, ABODY OF LOW MELTING METAL, AND A PLURALITY OF ARCUATE CLAMPS HAVINGINTERNAL BEARING FACES, THE SAID FACES BEING PORTIONS OF A FRUSTO-CONICSECTION SUBSTANTIALLY CORRESPONDING TO THE FRUSTOCONIC SECTION OF THEANODE, THE PAN HAVING A SOCKET RECEIVING THE LOWER END OF THE ANODE,SAID SOCKET BEING LARGER IN LATERAL AREA THAN THE ANODE, BUT HAVINGINTEGRAL REGISTRATION MEANS AT THE LOWER PART CONTACTING AND CENTERINGTHE ANODE END IN A LATERAL PLANE, THE BODY OF LOW MELTING METALPARTIALLY FILLING THE SPACE IN THE SOCKET NOT OCCUPIED BY THE ANODE, THECLAMPS SURMOUNTING AND ATTACHING TO THE PAN AND RETAINING THE ANODE INVERTICAL ALIGNMENT.